The most common method for non-invasive arterial blood pressure measurement uses an inflatable cuff which circumscribes an extremity, typically an upper arm. Once attached, the air pressure within the cuff is increased to a value well in excess of typical systolic pressure. As the air is controllably released, blood pressure is estimated by detecting "Korotkoff" sounds using a stethoscope placed on the limb near the artery. Those sounds are produced by disturbances in the arterial blood flow due to partial occlusions of the artery caused by the externally applied cuff pressure. As the cuff pressure is reduced the systolic pressure equals the cuff pressure at the time the first Korotkoff sound is detected. The diastolic pressure is identified when silence occurs. Manual pressure readings for systolic and diastolic pressure are determined by noting the scale value in millimeters of the height of a mercury column, or the pointer on an aneroid pressure gauge, which is pneumatically connected to the cuff air pressure. Devices of this type are commonly referred to as "sphygmomanometers."
In order for the above-described sphygmomanometer to yield accurate diagnostic readings, the cuff must have a width appropriate to the circumference of the patient's limb to which the cuff is applied. Most cuffs in use today comprise an elongated inflatable bladder with VELCRO.RTM. hook and loop fastener sections at each end. In my prior U.S. Pat. No. 5,243,991, the disclosure of which is incorporated herein by reference, there is disclosed an adjustable blood pressure cuff and a method of measuring blood pressure. My prior cuff and method avoid the errors resulting from using a blood pressure cuff having an improper width in relation to the circumference of the limb of the patient whose blood pressure is to be measured. That is accomplished by providing a flexible bladder which is foldable upon and removably retained to itself by means of hook-and-loop fasteners, such as Velcro.RTM. fasteners, attached to both sides of the bladder. In this way, a cuff width, such as 0.4 times the circumference of the limb as recommended by the American Heart Association, can be set by folding over and removably securing the hook-and-loop fasteners to achieve the appropriate cuff width. Critical diagnostic errors may arise if a cuff of improper width is utilized.
In addition to the width requirement, the inflatable cuff should be of a length which allows it to completely circumscribe the extremity to which is it is being applied without excessive overlap. Preferably, the length of the inflatable bladder should be somewhat larger than the circumference of the limb to which it is to be applied. If the cuff is too short, it may be difficult to apply, or if applied could be so tight as to be uncomfortable to the patient or prevent Korotkoff sounds from being detected. If the cuff is too long for the particular limb circumference to which it is applied, it may be difficult to secure the cuff, and thus may render it difficult to obtain the requisite pressure needed to occlude the artery and measure the patient's blood pressure.
Because of the importance of using a properly fitted cuff to yield accurate blood pressure readings, the American Heart Association recommends that a number of different-sized cuffs be maintained and utilized by medical practitioners to accommodate the range of patient arm widths, from pediatric to large adult size. In particular, health care providers must typically maintain at least five different-sized blood pressure cuffs in each examination room to accommodate of the following patient populations: infant, pediatric, adult, and large adult, and an extra large cuff to circumscribe the thigh of a patient whose pressure is being measured at the femoral artery.
Maintaining five or more separate blood pressure units is both expensive and cumbersome, especially in a clinical setting where many rooms need to be equipped with a full set of cuffs. Conventionally, each blood pressure unit has its own inflation bulb and aneroid gauge, thereby adding to its expense. If use of a more accurate wall mounted mercury manometer is employed, the appropriate blood pressure unit must be mechanically coupled and uncoupled to the manometer which often leads to difficulty because of jamming, misplaced tools and missing cuffs. Furthermore, storing five or more complete cuffs can be disadvantageous, especially in cramped quarters, such as an ambulance, "medivac" helicopter, military field hospital or the like.
Accordingly, it would be desirable to provide a single blood pressure cuff system which has appropriately sized blood pressure cuffs that can be used to accurately measure the blood pressure of infants, children, adults, and large adults, at both the brachial and femoral arteries, in a manner which is convenient, economical, conserving of space, and not susceptible to the other disadvantages mentioned above.